# -*- coding: utf-8 -*-

#   Copyright (c) 2010-2017, MIT Probabilistic Computing Project
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.

from .sqlite3_util import sqlite3_quote_name


def bayesdb_nullify(bdb, table, value, columns=None):
    qt = sqlite3_quote_name(table)
    if columns is None:
        cursor = bdb.sql_execute('PRAGMA table_info(%s)' % (qt,))
        columns = [row[1] for row in cursor]
    changes = bdb._sqlite3.totalchanges()
    for column in columns:
        qc = sqlite3_quote_name(column)
        bdb.sql_execute('UPDATE %s SET %s = NULL WHERE %s = ?' % (qt, qc, qc),
            (value,))
    return bdb._sqlite3.totalchanges() - changes
